1. Technical Field
The present invention relates to a projector.
2. Related Art
Projectors are capable of displaying large screen images, and therefore, draw attention not only as display devices for presentation, but also as image display devices for displaying images required to have high quality, such as movies. Therefore, in the projectors, growth of resolution of light modulation elements is in progress, and there is a tendency of ever-growing sizes of the light modulation elements. The growth of the light modulation element sizes causes growth of sizes of overall optical systems, which incurs growth of the sizes of the projectors, and at the same time, increase in cost.
The lower limit of the pitches of the pixels constituting the light modulation elements is generally believed to be in a range of 8 through 9 μm. Therefore, in order for obtaining the resolution of, for example, 4K2K (assumed to be 4096 pixels in the lateral direction×2160 pixels in the vertical direction), the size (the diagonal length) of the area (referred to as an image display area) available for image display in the light modulation elements needs to be equal to or greater than 1.6 inch.
FIGS. 6A and 6B are diagrams showing a configuration of the light modulation element and the optical system in the periphery thereof in a typical projector in the related art. It should be noted that FIG. 6A is a perspective view, and FIG. 6B is a plan view corresponding to FIG. 6A, namely a diagram of the configuration shown in FIG. 6A viewed from a direction along the arrow a.
As shown in FIGS. 6A and 6B, in the typical projector, the light modulation elements 100R, 100G, and 100B corresponding respectively to red (R), green (G), and blue (B) are each disposed so as to have the long side in the horizontal direction (the direction of the x-axis or the y-axis among the x, y, and z-axes shown in FIG. 6A) and the short side in the vertical direction (the vertical direction in FIG. 6A, namely the direction of the z-axis among the x, y, and z axes). In other words, the light modulation elements 100R, 100G, and 100B are arranged so that one of the short sides of the light modulation element 100R and one of the short sides of the light modulation element 100G are adjacent to each other, and further the other of the short sides of the light modulation element 100G and one of the short sides of the light modulation element 100B are adjacent to each other, in a similar manner. Further, in this case, in the positional relationship between the light modulation elements 100R, 100G, and 100B, and a cross dichroic prism 110 as a combining optical system, each of the short sides of each of the light modulation elements 100R, 100G, and 100B is disposed along a height direction (the z-axis direction) of four triangular prisms forming the cross dichroic prism 110.
It should be noted that the light modulation elements 100R, 100G, and 100B are arranged to modulate the R, G, and B colored light beams, respectively, based on image data, and the colored light beams modulated by the respective light modulation elements 100R, 100G, and 100B are combined by the cross dichroic prism 110 to be output as image light. The image light emitted from the cross dichroic prism 110 is then projected by a projection optical system 120 on a projection screen, not shown, as a landscape image.
Further, to the light modulation elements 100R, 100G, and 100B, there are respectively connected signal line cable substrates 130R, 130G, and 130B each having various signal lines such as a data line for supplying the image data and a control line for supplying a control signal, printed thereon. It is general that these signal line cable substrates 130R, 130G, and 130B are each formed of a flexible printed circuit board, and connected respectively to the long sides of the light modulation elements 100R, 100G, and 100B. It should be noted that the signal line cable substrates 130R, 130G, and 130B are hereinafter referred to as FPC boards 130R, 130G, and 130B, respectively.
In the typical projector of the related art, the light modulation elements 100R, 100G, and 100B, and the cross dichroic prism 110 have the configuration shown in FIGS. 6A and 6B. Therefore, assuming that each of the light modulation elements 100R, 100G, and 100B has a resolution of, for example, 4K2K, the diagonal size of the image display area in each of the light modulation elements 100R, 100G, and 100B is about 1.6 inch as described above. The size of the cross dichroic prism 110 in the case of using such light modulation elements needs to be about 60 mm (one side L1 of the square composed of end surfaces of the respective four triangular prisms)×60 mm (the other side L2 of the square composed of end surfaces of the respective four triangular prisms)×35 mm (the height H of the triangular prisms), and further, the lens diameter of the projection optical system 120 needs to be equal to or greater than 70 mm. It should be noted that, assuming that the lens diameter of the projection optical system is 70 mm, the F-value of 2.5 can be achieved in the design giving priority to the brightness of the lens of the projection optical system.
As described above, in the typical projector of the related art, the higher the resolution of the light modulation element is, the further the growth of the sizes of the cross dichroicprism 110 and the projection optical system 120 proceeds, which forms a factor causing decrease in the productivity of these optical elements and increase in the cost thereof.
To cope with the above, it is possible to arrange the light modulation elements 100R, 100G, and 100B so that the long sides of the respective light modulation elements 100R, 100G, and 100B are adjacent to each other while keeping the direction of the long sides of the respective light modulation elements 100R, 100G, and 100B to be the horizontal direction (the lateral direction in FIG. 7A) as shown in FIG. 7A. In this case, the light modulation elements 100R, 100G, and 100B have the arrangement in which each of the long sides of each of the light modulation is disposed along the height direction (the x-axis direction) of the four triangular prisms constituting the cross dichroic prism 110. It should be noted that FIG. 7A is a perspective view of the light modulation elements 100R, 100G, and 100B arranged so that the long sides thereof are adjacent to each other, and FIG. 7B is a side view corresponding to FIG. 7A, namely the diagram of the light modulation elements viewed in a direction along the arrow b.
By arranging the light modulation elements 100R, 100G, and 100B so that the long sides thereof are adjacent to each other as shown in FIGS. 7A and 7B, the size of the cross dichroic prism 110 becomes about 35 mm (one side L1 of the square composed of end surfaces of the respective four triangular prisms)×35 mm (the other side L2 of the square composed of end surfaces of the respective four triangular prisms)×60 mm (the height H of the triangular prisms) even in the case with the light modulation elements having the same resolution as that of the light modulation elements 100R, 100G, and 100B shown in FIGS. 6A and 6B. Further, the lens diameter of the projection optical system becomes about 45 mm. Therefore, the volume of the cross dichroic prism 110 can be reduced to about 60% of that in the case shown in FIGS. 6A and 6B. Further, in this case, it is possible to achieve the F-value of 2.0 by designing the lens diameter of the projection optical system to be 50 mm, and therefore, downsizing is thought to be possible while keeping the same performance as in the case shown in FIGS. 6A and 6B.
However, if the light modulation elements 100R, 100G, and 100B are arranged so that the long sides thereof are adjacent to each other, there arises a problem that at least one of the FPC boards 130R, 130G, and 130B connected respectively to the light modulation elements 100R, 100G, and 100B shields the light input from a light source to the respective light modulation elements 100R, 100G, and 100B, thus the light from the light source is prevented from appropriately entering the light modulation elements 100R, 100G, and 100B, respectively.
FIG. 8 is a diagram schematically showing a general configuration of the optical system of the projector in the case in which the light modulation elements 100R, 100G, and 100B are arranged as shown in FIGS. 7A and 7B. As shown in FIG. 8, the light from the light source 140 is separated by a first dichroic mirror 151 into the red light (R), the green light (G), and the blue light (B), and the blue light (B) thus separated is input by a mirror 161 to the light modulation element 100B while the red light (R) and the green light (G) thus separated from the blue light (B) is separated by a second dichroic mirror 152 into the red light (R) and the green light (G). Further, the green light (G) separated by the second dichroic mirror 152 is input to the light modulation element 100G while the red light (R) is input by mirrors 162, 163 to the light modulation element 100R.
In the optical system shown in FIG. 8, when considering, for example, the light modulation element 100G corresponding to the green light (G), the FPC board 130G is coupled to the lower long side of the light modulation element 100G as shown in the drawing in the light modulation element 100G of the green light (G), and consequently, shields the blue light (B) separated by the dichroic mirror 151.
It should be noted that although the FPC board can be curved or bent within an appropriate angle, if the FPC board is bent at an excessively acute angle or an excessive twist or the like is applied to the FPC board, a broken line or the like might be caused. Therefore, the FPC board needs to be connected to other devices in a manner not providing the FPC board with folding with an excessively acute angle or an excessive twist. Therefore, if the light modulation elements 100R, 100G, and 100B are arranged so that the long sides thereof are adjacent to each other, at least one of the FPC boards 130R, 130G, and 130B should exist on the light path as shown in FIG. 8.
As a method for coping with this problem, it is possible to connect the FPC boards 130R, 130G, and 130B to the short sides of the respective light modulation elements 100R, 100G, and 100B. For example, JP-A-11-249070 (Document 1) shows a technology (hereinafter referred to as a related art technology) of arranging the light modulation elements so as to have the long sides adjacent to each other, and at the same time connecting the FPC boards to the short sides of the respective light modulation elements. By thus arranging the light modulation elements so as to have the long sides of the respective light modulation elements adjacent to each other, downsizing of the cross dichroic prism becomes possible, and further, by connecting the FPC boards to the short sides of the respective light modulation elements, it becomes possible to remove the FPC boards connected to the respective light modulation elements from the light paths of the respective colored light beams, thus an advantage of preventing the FPC boards from shielding the colored light beams can be obtained.
However, if it is arranged to connect the FPC boards simply to the short sides, there arises the following problem. The scanning direction for image data writing in the typical projector is set to be parallel to a direction (referred to as a long side direction) along the long side. Therefore, in the case of the light modulation element having a resolution of 4K2K, 4096 signal lines disposed along the long side are necessary for providing each of the pixels of the light modulation element. Therefore, if the FPC board is connected simply to the short side thereof while keeping the scanning direction for image data writing to the long side direction, a wiring space for leading the 4096 signal lines to the FPC board provided on the short side is required. This causes growth in overall size of the light modulation element.
FIGS. 9A and 9B are diagrams schematically showing the arrangement of the signal lines of the light modulation element. Although the light modulation element 100G for the green light (G) is shown in FIGS. 9A and 9B, the light modulation elements 100R and 100B for the red light (R) and the blue light (B) have substantially the same configurations. It should be noted that FIG. 9A shows the typical light modulation element having the FPC board 130 coupled to the long side thereof, and in this case, there is adopted a configuration in which the 4096 signal lines from the FPC board 130G are connected to a data line driver 102 disposed along the long side (the long side of the image display area 101) of the light modulation element 100G. It should be noted that in the configuration, a gate line driver 103 is disposed on the short side (the short side of the image display area 101) of the light modulation element 100G, and a few signal lines for control from the FPC board 130G are connected to the gate line driver 103.
FIG. 9B shows the case in which the FPC board 130G is coupled to the short side of the light modulation element 100G shown in FIG. 9A. In the case in which the FPC board 130G is coupled to the short side of the light modulation element 100G, the wiring space (the area A surrounded by the dotted frame in the drawing) for leading the 4096 signal lines connected to the data line driver 102 disposed on the long side to the FPC board 130G coupled to the short side is required as shown in FIG. 9B. Since an area of at least 10 mm in size in the z-axis direction shown in the drawing is required as the wiring space, which causes the growth in the overall size of the light modulation element.
Therefore, if the FPC boards are simply coupled to the short side while keeping the long side direction of the light modulation elements 100R, 100G, and 100B to the scanning direction for the image data writing, it is hardly possible to make the most use of the advantage obtained by disposing the light modulation elements 100R, 100G, and 100B so as to have the long sides adjacent to each other, namely the advantage of making it possible to downsize the cross dichroic prism and the projection optical system.